Firefighters, industrial workers, law enforcement and the like, need garments that protect them from a variety of threats. These workers need protection from extreme weather conditions, hazardous liquids, heat and flame. In particular, protection from flame requires materials that both self-extinguish and prevent burn caused by heat transfer through a garment. In addition, liquid and flame protection clothing should have a level of breathability sufficient to reduce heat stress burden to extend their ability to perform the function or to prevent heat casualty.
A variety of flame protective materials have been developed which are self-extinguishing in character. Most notable are the meta-aramids, modacrylics, polybenzimidazole (PBI), polybenzoxazole (PBO), para-aramids, poly diimidazo pyridinylene dihydroxy phenylene (PIPD), melamine, flame resistant (FR) polyester, FR rayon, and FR cotton, to name a few. However, to provide suitable insulation (to reduce burn caused by heat transfer), most commonly thermally stable insulative layers are added. For instance, in structural firefighting, the turnout clothing is typically comprised of a thermally stable, self-extinguishing shell, a moisture barrier (to provide liquid protection), and a thermal liner (to provide insulation from heat and flame). Insulation that protects users from extremes in temperature by increasing thickness is well known. However increased insulation achieved with increased thickness tends to adversely affect the user's heat stress burden under high work rate or high heat environments.